1. Field of the Invention
The present invention relates to an elastic crawler employed in a crawler-mounted traveling device used as a traveling unit for construction and engineering equipment or agricultural equipment.
2. Description of the Related Art
A conventional crawler-mounted traveling device includes a driving sprocket disposed either on front or rear side in the direction of travel, an idler disposed on the other side, a plurality of rollers disposed between the driving sprocket and the idler, and an endless belt-shaped rubber crawler (crawler belt) wound around the driving sprocket, the idler, and the tracker rollers, wherein the rubber crawler is circulated in a circumferential direction thereof by rotating the driving sprocket.
An endless crawler body of the rubber crawler is formed of rubber, and the crawler is provided with a tension member embedded circumferentially of the crawler because a significantly large force (tension) is exerted on the rubber crawler in the circumferential direction thereof.
A conventional tension member is constructed by disposing a multiplicity of tension cords having opposite ends in parallel to each other in a widthwise direction of the crawler body, and winding around the crawler body one full circle in the circumferential direction of the crawler (See JP-A-2000-103374).
In this tension member, each tension cord is formed into a loop by overlapping and joining its opposite ends in a thicknesswise direction of the crawler in the crawler body (lap joint).
As shown in FIG. 6A, which corresponds to JP-A-2000-103374, in a tension member 16 in which longitudinally (the circumferential direction A of the crawler, and referred simply as the “circumferential direction A”, hereinafter) opposite edges 16a are cut along the direction orthogonal to the circumferential direction A and overlapped, longitudinal ends of tension cords 17 are linearly aligned in a widthwise direction B of the crawler (hereinafter, referred simply as the “widthwise direction B”) Therefore, it is obvious that bending rigidity of the tension member around the boundaries is significantly different between a single-ply portion (a portion of the tension member which is not overlapped) and a double-ply portion (a portion of the tension member which is overlapped). This results in an extreme variation in bending rigidity in the circumferential direction A, and thus improvement of the rubber crawler has been required.
In order to solve the problem of bending rigidity, the edges 16a of the tension member 16 in the circumferential direction A are cut diagonally with respect to the widthwise direction B, as shown in FIG. 6B.
In the tension member 16 shown in FIG. 6B, which corresponds to JP-A-2000-103374, since the ends of the tension cords 17 are aligned diagonally with respect to the widthwise direction B, the variation in rigidity around the boundaries between the single-ply portion and the double-ply portion in the circumferential direction A is alleviated. However, since a distance T in the circumferential direction A from one end to the other end of the longitudinal edge 16a of the tension member 16 in the circumferential direction A is smaller than an overlapping length L of an overlapped portion 18 of the tension member 16 (T<L) in the circumferential direction A, the tension member 16 is overlapped entirely in the widthwise direction B in the area shown by a letter J in FIG. 6B, and thus significant improvement of bending rigidity cannot be expected.